Screw extractor



Jmme 21, 1938.. E. F. JACFKMAN Filed July l,- 1936 2 Sheets-Sheet l Snventor L i/W571? F? JACK/VAN [6) I TM attorney- Patented June 21, 1938 UNITED STATES PATENT OFFICE 2.121.197 sonnw Exrasc'roa Elmer F. Jackman, The Ridge Tool Ridgeville, Ohio.

Application July 1, 1936, Serial No. 88,425

4Claims.

This invention relates to improvements in extractors particularly adapted for removing the embedded parts of broken stud bolts and the like which. have had their heads or ends broken oil.

Heretofore there have been many stud extractors, the most common type of which had tapered shanks with reversely twisted flutes and ribs. The end is usually provided with a square for receiving a wrench. Practically all of the extractors are operated by drilling a hole in the object to be removed, when there is no hole, and inserting the extractor in the hole and turning the extractor with a wrench. The ribs grip the edges of the hole and the broken stud is thus unscrewed. There are, however, times when the extractor fails to remove the broken stud, particularly when it has become rusted in position.

The cause of the failure is often due to the extractor failing to obtain suiiicient grip upon the stud.

Another common cause for failure is because the tapered extractors have a spreading action upon the object being removed and hence the bore in the article must be relatively small to leave a large and strong wall thickness. Obviously then the extractor must be relatively small and when the small extractor is used it becomes wedged in the bore and breaks 011 before willcient torque can be applied to remove the stud. The short zone of engagement, usually at the edge of the bore, being of insufficient length to permit the necessary torque to be applied, the result being that the extractor merely mutilates the edge of the bore.

In the extractor of my present invention I have eliminated a great many of the defects of the prior art devices and have provided an ext'ractor which will readily remove studs that were heretofore extremely hard or impossible to remove. This is accomplished by providing an increased area of gripping surfaces which allows more torque to be applied and which does not cut or mutilate the bore in the studor nipple.

The tightest gripping thread is easier to remove if the wall of the stud can be reduced to a mere shell, as contemplated in the present invention, and still permit an extractor to be used which has a grip upon the shell that does not expand the shell. In drilling out the stud for my extractor, the hole may be drilled entirely through the stud and of such size as to remove substantially 90% of the metal. Removing this metal makes the stud much easier to remove and permits a large diameter tool to be used which cannot break.

Another feature of the invention resides in providing a means whereby the torque applied by a wrench to the extractor can be applied at 5 a point close to the point of greatest resistance rather than at the extremity, lessening the tendency for the device to break and increasing the efficiency with which the torque is applied. Furthermore the construction is such that should the device be-broken itis still capable of being used as an extractor by a very simple grinding operation. Certain economies in manufacture will also be apparent.

Still other advantages of the invention, and the invention itself, will become more apparent from the following description of some embodiments thereof, which description is illustrated by the accompanying drawings.

- In the drawings:

Fig. 1, is an enlarged elevational view of an extractor embodying my invention, showing the same in position in .a broken stud, the stud and container being shown in section;

Fig. 2 is'a section taken on the line 2-2 of Fig. l;

Fig. 3 is an enlarged elevational view of the torque applying member for the extractor with the friction spring removed;

Fig. 4 is a vertical section through the torque 30 applying member of Fig. 3, showing the friction spring in place;

. Fig. 5 is a plan view of the friction spring for the torque applying member; i

Fig. 6 is an elevational view of a modified 35 form showing the same prior to insertion in a stud;

Fig. 7 is a similar view to Fig. 6 showing the device after insertion;

Figs. 8, 9 and 10 are enlarged cross sectional views of modified formsof the invention, showing in dotted lines the bore into which they are adapted to be driven;

Fig. 11 is a cross section of another modified form; and

Fig. 12 is an enlarged cross section of a portion of an extractor showing the eilect of its engagement in a bore.

As best shown in Fig. 1, there is illustrated the end of a stud i which is broken off in a 50 threaded aperture oi a member 2 and. which piece of stud is to be removed. A bore 3 is first drilled through the remaining end of the stud, into which the tool of my invention may be driven to permit the stud end to be unscrewed.

tool in the preferred form ofmy invencomprises an elongated cylindrical shank I straight ribs extending longitudinally and parallel to each other. of varying number and comaces I, each of which subtends of substantially greater than 90' to the cylindrical body at the base The two faces meet in an apex at extremities of the rib. The end of the tool is d.asbestshown at llinl ig. 1,toasubstansemi-spherical form to providea self-centering point for starting The diameter of the bore is slightly larger than the diameter of cylindrical shank to provide a slight clearance between the body and the bore engagethematerialatthesideoftheboreand enthetool lsdrlven intothebore,andthematerial may bedisplacedlaterallyasatli,l 'ig.l2.

shank cylindrical and the ribs the bore being cylin-.

ggs

It for the redeption of a applying torque to thetool for operating the same.

For the smaller sized tools, however, I provide a torque-transmitting member for turning the extractor, which comprises a hexagonal slide it, asbestshowninl'lgs.3and4forreceiving beusedontheiargersisesofextractorif slide against the extractor and thus supplies frictional engagement to keep the slide in any desirableposl tion. "Ihetoolhavingbeendrivenhomeinthebore,

stud to be removed and a wrench applied to the hexagonal exterior surface of the slide throughwhich torqueistransmittedto the tool. 'Ihisisofconsiderableadvantagaespe'ciallvin small tools inasmuch as the Anplyln thegreatesttorque indicatedbytheposition of the llideinl'lg. thetorque nearesttothe point of resistance. tending to eliminate Inthcuseofsmallsiaeextractorsforremovmallstudathetorqueslideisparticularly furnishesalargegripforthe the tool into the bore.

movided, particularlyin the larger sizes,

turningwrenchandalsomakesitto grindthesquareontheendofthetoolasin Fig. 6 for reception of a wrench and hence weaken the shank.

The ribs having cut their .own grooves into the material of the stud provide a long gripping sur- "face; the frictional engagement thus gained isso great that the most stubborn cases are relatively easy to remove. Inasmuch as the force applying face is at an obtuse angle to the direction of rotation there is not the tendency for the tool to cut and remove chips, as is the common experience in the ordinary type of extractors, and since the cylindrical body substantially nlls the borethere is no place for material to go which mayhave a tendency to be removed. By providing the extractor with longitudinally extending ribs or uniformity throughout its length, in event of breakage thelarge remaining piece may readily have its broken and ground as on the original device, and the extractor again used in the usual manner. This re-grinding process can be continued until the extractor be comm too short for further'value.

In Figs. 6 and '1 there are shown two views of one of the larger size extractors prior to and after insertion in the bore of a stud. It will be noted that the bore of the stud is substantially smaller than the diameter through the apexes of the ribs, and that the ribs therefore must cut their own way into the wall of the stud. Thus at II. The end ii is beveled to provide a starting Fig. 8. shows an extractor having a cross section where the body I is hexagonal in shape stantially the same, the contour of the ribs beingsubstantiallythesameasinligs. land2. The face of the rib, which is the driving face for the object being removed, is at an'angle of greater than 90 to the direction of rotation of the article being removed.

In Fig. 9 there is shown in cross section a modified structure which is very similar to Fig. 8 except that the body I" is slightly smaller and the ribs are so placed at the intersection of the faces that the leading face 25, the tool being adapted particularly for removing studs or the like having right hand threads, is somewhat longer than the following face 28. This provides a removing rib having a large area for exerting force and backed up to a greater extent by the wall 11 of the body. 7

Fig. 10 is a cross sectional view of a device substantially like that in Figs. 1 and 2 except that the body of the tool is cut away at the base of eachrib along a cord ll of the body to provide greater room for displacement of the material of the stud.

'Fig. 12 is an enlarged view of the device of Fig. 8 showing how the flutesdisplace the wall of the' stud to be removed.

Fig. 11 is substantially the same as Fig. 10 except thatinsteadofaflatsurface, agroove ll oneachside oftherlbslsprovidedtopermit the material of the stud being removed to be displaced and enter therein.

In manufacturing this device, particularly that of Fig. 1, it is readily made from stock formed in the desired configuration of cross section in relatively long lengths, after which the desired sizes of sections may be severed therefrom and the insertion ends properly trimmed to provide the individual extractors. This results in considerable economy since machining operations are practically eliminated.

Having thus described my invention I am aware that numerous and extensive departures may be made therefrom but without departing from the spirit of the invention.

I claim:

1. An extractor for removing threaded objects from threaded engagement in a bore or the like comprising a body of cylindrical form throughout its length and of a diameter providing a sliding fit with an axial bore in the object, to be removed, a plurality of straight bore-engaging ribs of V-shaped cross-section and uniform height extending longitudinally throughout the length of the body and adapted to be driven into the wall of said bore in the object to be removed.

2. An extractor for removing threaded objects from threaded engagement in a bore or the like comprising a body of cylindrical form throughout of the body and adapted to be driven into the wall of said bore in the object to be removed, a torque transmitting member having a bore conforming to the exterior surface of said body and slidable longitudinally thereon, and an exterior surface on said member for application of a wrench to permit the torque applied to the body to be localized near the point of greatest resistance.

from threaded engagement in a bore or the like comprising a body of cylindrical form throughout its length and of a diameter providing a sliding fit with an axial bore in the object to be removed, a plurality of straight bore-engaging ribs of V-shaped cross-section and uniform height extending longitudinally throughout the length of the body and adapted to be driven into the wall of said bore in the object to be removed, a torque transmitting member having a bore conforming to the exterior face of said body and slidable longitudinally thereon, and an exterior surface on said member for application of a wrench to permit the torque applied to the body to be localized near the point of greatest resistance, friction means carried by the sleeve to maintain the same in the desired longitudinal position on said body, comprising a spring having an end adapted to extend through-the sleeve and engage the surface of the body.

4. In an extractor for studs, nipples or the like comprising an elongated cylindrical shank adapted to be disposed in a bore formed in the object to be removed, the body of said shank being-of a size to substantially fill the bore, a. plurality of straight ribs disposed about the straight surface of the shank extending longitudinally along the shank and parallel to each other, each rib having two oppositely disposed faces meeting at an edge, and each face disposed at an angle of greater than 90 to the axis of rotation, and adapted to be driven into the wall of said bore, a torque transmitting member for said shank comprising a hexagonal sleeve having a bore through it conforming to the surface of the shank and adapted to slide freely upon the shank, a circumferential groove disposed about said sleeve adjacent one end thereof, and an aperture formed in said groove extending into the bore of the sleeve, a spring member seated in said groove, and having an end extending through said opening into 'said bore, and adapted to engage said shank and hold the sleeve in frictional sliding engagement with said shank.

ELMER F. JACKMAN. 

